The invention relates generally to ion beam systems, and more specifically to plasma ion sources of the ion beam systems, particularly beam extraction from the ion sources.
As the dimensions of semiconductor devices are scaled down in order to achieve ever higher level of integration, optical lithography will no longer be sufficient for the needs of the semiconductor industry. Alternative “nanolithography” techniques will be required to realize minimum feature sizes of 0.1 μm or less. Therefore, efforts have been intensified worldwide in recent years to adapt established techniques such as X-ray lithography, extreme ultraviolet lithography (EUVL), and electron-beam (e-beam) lithography, as well as newer techniques such as ion projection lithography (IPL) and atomic-force-microscope (AFM) lithography, to the manufacture of 0.1 μm-generation complementary metal-oxide-semiconductor (CMOS) technology. Significant challenges exist today for each of these techniques: for X-ray, EUV, and projection ion-beam lithography, there are issues with complicated mask technology; for e-beam and AFM lithography, there are issues with low throughput.
Focused ion beam (FIB) patterning of films is a well-established technique (e.g. for mask repair), but throughput has historically been a prohibitive issue in its application to lithographic processes in semiconductor manufacturing. A scanning FIB system would have many advantages over alternative nanolithography technologies if it can be made practical for high volume production. Such a system could be used for maskless and direct (photoresist-less) patterning and doping of films in a semiconductor fabrication process. It would be necessary to focus the beam down to sub-micron spot sizes.
U.S. Pat. No. 5,945,677 to Leung et al. issued Aug. 31, 1999 describes a compact FIB system using a multicusp ion source and electrostatic accelerator column to generate ion beams of various elements with final beam spot size down to 0.1 μm or less and current in the μA range for resist exposure, surface modification and doping.
Conventional FIB columns consist of multiple lenses to focus the ion beams. In order to get smaller feature size, small apertures have to be used to extract the beam and at the same time act as a mask. For the extraction of ions from a plasma source using a long, narrow channel, aberration is always a problem because of the edge effect.